Question

How to adjust ph of 0.001 n hcl by using hcl and naoh?

Answer 1

pH of 0.001 N NaOH = 11

So, the pH of the NaOH Solution should be lowered to 10 which would be pH=10

The weight of NaOH present in 10 ml.of 0.001N NaOH=0.001 x 40/100= 4 x 10–4

If the concentration of the NaOH is 0.0001

then it's pH will be 10!

10 ml.of 0.001M NaOH will contain

=10 x 0.001=0.01 m.mole.

But if you add 8.1 ml.of HCl, then it will add 0.0081 m.moles of HCl, in the mixture and the resulting Solution will contain (0.01–0.0081)= 0.0019 m.moles of NaOH in 18.1 ml.!!!. The concentration will be =0.0019/18.1=0.000105 N. Now the pH will be 1 unit lower. ie., approximately =10.

But accurately it is

=- log(0.000105)=14–3.9788=10.02. OK.